This section provides background information related to the present disclosure which is not necessarily prior art.
Rotary shaft seals have been used in machinery, the automotive industry, as well as other industries. For example, such applications can include use on transmissions, pinions, gears, axles, etc. that require a symmetrical functioning dynamic seal (i.e., the seal must function effectively in both directions of shaft rotation). The seal has an air side and a lubricant or oil side. The seal helps maintain the lubricant (e.g., oil) on the lubricant side. Lubricant may, however, leak from a lubricated side to the non-lubricated (air) side through the interaction of the active surfaces of the seal with the shaft. Spiral grooves or built-up ribs (hereinafter collectively referred to as “grooves”) disposed on the active side of the seal capture the leaked lubricant and hydrodynamically pump the lubricant back into the lubricated side due to relative rotation between the seal and the shaft about which the seal is disposed.
Typically, the grooves are arranged in a spiral or helical configuration on the shaft, contacting side of the seal. In order to enable hydrodynamic pumping of captured lubricant, the grooves spiral along the active surface of the seal in opposite directions to accommodate relative rotation between the shaft and the seal regardless of the direction of the relative rotation. The grooves are open at the lubricant side of the seal and communicate with the lubricant therein. Having the grooves at the lubricant side of the seal creates potential problems. For example, static oil leaks can develop. Additionally, air leakage during pressurization testing of the machinery on which the seal is being used at the end of the assembly stage can also occur. Accordingly, it would be advantageous to provide a dynamic seal having a bi-directional pattern thereon to capture lubricant that leaks past the seal edge and returns the same to the lubricant side of the seal. Furthermore, it would be advantageous if such a dynamic seal minimized and/or avoided the drawbacks mentioned above.
A dynamic laydown lip seal according to the principles of the present disclosure includes two opposite sets of spiral grooves separated by a small static band all on the contact surface of the seal where the seal engages the shaft. When the shaft rotation direction is causing the oil side grooves to pump oil toward the oil side, the oil cannot reach the air side grooves, thus, the air side grooves are not hydrodynamically engaged and the seal maintains normal function. When the shaft is rotating in the opposite direction, the oil side grooves will be pumping oil toward the air side past the static dam with a first pump rate. When this oil flow overwhelms the static band, the oil gets into the air side pumping grooves hydrodynamically engaging them wherein the air side pumping grooves pump the oil back towards the static dam and towards the oil side. The air side spiral grooves are designed to provide greater pumping capacity than the oil side spiral grooves so that the net effect is that the oil that passes the static dam is continually returned toward the oil side by the higher capacity air side spiral grooves.
The individual grooves of the oil side and air side sets of spiral grooves can be symmetrical in shape and the number of grooves in the air side set of grooves can exceed a number of grooves in the oil side set of grooves so that the capacity of the set of air side spiral grooves exceeds the capacity of the oil side spiral grooves.
The air side set of spiral grooves can include grooves that each include a booster zone adjacent the static band wherein in the booster zone the grooves reduce in cross-sectional area as the grooves get closer to the static dam. This booster zone can cause an increase in the pressure on the air side of the static dam causing the oil on the oil side of the static dam to be pushed back towards the oil side.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.